Mortgage delinquencies in the Bay Area are higher than the national average but lower than the California average, according to a report being released today.

Of mortgaged homes, 7.97 percent were behind on payments by more than 60 days in the San Francisco metropolitan area (the counties of San Francisco, Alameda, Contra Costa, Marin and San Mateo) in the second quarter, according to TransUnion, one of the nation's three big credit bureaus. That was up from a 7.07 percent rate a year earlier.

Nationally, 6.67 percent of home borrowers were "seriously delinquent," as being overdue by 60 or more days is termed. In California, the number stood at 10.45 percent.

"The effects are not as severe in San Francisco (area) as elsewhere in California," said Ezra Becker, director of consulting and strategy for TransUnion in Chicago. "San Francisco is a nice place to live; home depreciation hasn't been as severe here."

Home depreciation and unemployment are the two strongest factors influencing mortgage delinquencies, Becker said.

He quoted data from Economy.com showing that the median home value in the five-county San Francisco metro area now stands at $504,000, down 33 percent from $751,000 in early 2006. Home values in Los Angeles fell 45 percent in the same time period, while those in foreclosure-ridden Las Vegas plunged 55 percent, he said.

TransUnion predicts that the five-county San Francisco metro area serious-delinquency rate will dip to 7.79 percent by the end of the year. It expects the national serious-delinquency rate to edge down to 6.4 percent by year end. But for California, it expects the rate to rise to 10.69 percent by year end.

Looking at the nine-county Bay Area, the serious-delinquency rate ranged from 3.98 percent in Marin to 13.12 percent in Solano County. San Francisco was the second lowest in the region at 4.49 percent.

Historically, serious-delinquency rates have hovered between 1.5 percent and 2 percent but started to take off in mid-2007, TransUnion said.

Mortgage delinquencies

Percentage of mortgaged homes that were "seriously delinquent" - overdue by 60 days or more - in the second quarter, by county: